While comparing the setup of solid phase models in MFIX-TFM and Fluent-TFM, I’ve noticed a significant difference between the two. Fluent requires the specification of two phase fractions: friction packing limit and packing limit, while MFIX only requires the setting of a single phase fraction, i.e. packed bed void fraction.
Given that gas-solid flow can be treated as a non-Newtonian fluid, frictional forces play a primary role when the void fraction is below a certain threshold. And there should also be a packing limit to avoid an excessively small void fraction. I’m curious about the rationale behind MFIX-TFM’s approach of using only one phase fraction. I’m interested in understanding the implications of this choice for modeling solid phase.
I would greatly appreciate any insights or explanations on why MFIX only requires a single phase fraction setting. Thank you in advance for any information you can share.
In addition to understanding, I think more importantly, this is helpful for mfix users to switch from using fluent cases to simulating with mfix, as some of the cases in the paper were calculated using fluent.
The Schaeffer friction model doesn’t use a friction threshold. If you use the Srivastava and Sundaresan or the Guo-Boyce friction model, you can set the solids volume fraction at onset of friction:
I’ve noticed that when using the Schaeffer model in Fluent-TFM, it is still required to set two phase fraction thresholds, unlike in MFIX-TFM where such a threshold is not necessary. Could you provide a more in-depth explanation of this?
